The present practice in starting an internal combustion engine requires that all cylinders be activated during the starting sequence. This requires a starting motor and battery having sufficient capacity to provide the power required to overcome the inertia of the rotating parts of the engine as well as the compressive forces in all cylinders of the engine. Typically all of the cylinders are started in sequence which does not allow the starter motor time to store energy in the flywheel to help overcome the inertia forces of the operating parts of the engine.
A number of mechanically controlled valve actuating mechanisms have been tried to reduce the starting load on the engine. These systems generally relate to mechanical devices which initially open all of the exhaust valves to reduce the compressive load in all cylinders. Typical examples of this type of system are shown in U.S. Pat. No. 4,615,313, issued Oct. 7, 1986, titled "Automatic Decompression Device For Internal Combustion Engine;" U.S. Pat. No. 4,556,025, issued Dec. 3, 1985, titled "Engine Valve Mechanism Having Valve Disabling Device;" and U.S. Pat. No. 3,496,922, issued Feb. 24, 1970, titled "Compression Relief Mechanism." However, these systems generally open the exhaust valves in all cylinders and rely on centrifugal force to gradually close the valves, which reduces the potential starting success of all cylinders because of the lowered compression. These systems cannot discriminate and reduce the compression on some of the cylinders of multi-cylinder engines nor can they sequentially select the cylinder to be used for starting the engine.
In U.S. Pat. No. 4,550,704, entitled "Multi-Cylinder Internal Combustion Engine Having Disconnectable Groups Of Cylinders," issued on Nov. 5, 1985, a logic control unit is described which provides for alternate use of groups of three cylinders or all cylinders at increased loads. U.S. Pat. No. 4,875,443, issued on Oct. 24, 1989 and entitled "Start Control System for Internal Combustion Engine", relates to the use of an electronic control unit to inject a prestart fuel into the cylinder with a time delay period before activating the starter motor.
However, none of these patents disclose nor suggest a means to automatically reduce the starting load on an engine in order to reduce the size of the battery required to start the engine.